PURPOSE: To determine the efficacy of saline versus heparin flush solution to maintain peripheral i.v. locks in a pediatric population. METHOD: A prospective, randomized, double-blind design was used. A sample of 124 peripheral i.vs. were flushed with either saline or heparin in saline. Subjects were infants over 28 days of age and children. FINDINGS: The heparin and saline groups were comparable for total hours duration of the i.v. and for incidence of complications. CONCLUSIONS: Saline is efficacious in maintaining patency of peripheral i.v. locks in children over 28 days of age.